I haven’t played with imovie in about 20 years, but I know it wasn’t meant for things like Metadata. I recently used Premiere Pro’s metadata window to confirm when something important took place. I believe it had the time and date it was shot, and the camera settings. I would try that.
As far as batch renaming, I don’t know of anything for video clips. I have had to do that before. It’s not fun. What I did was copy the name of the clip and do a rename, and paste over everything but the clip number. Ex: Birthday_Pty-101.mov. Try that. I think it would be faster than a recapture.